In addition to a miniaturization trend of a wireless communication system, a demand for the next generation wireless communication receiver with flexibility, adaptability, and cognitivity has been increased. In order to satisfy this demand, Analog-to-Digital Converter (ADC) needs to be placed as close as possible to an antenna and frequency conversion and demodulation functions are performed using a Digital Signal Processor (DSP). As the next generation wireless communication receiver satisfying the above demand, a bandpass sampling receiver receives considerable attentions. The bandpass sampling receiver may provide excellent functions in aspects of reconfiguration and multiband/multimode reception.
A typical bandpass sampling receiver may receive an analog RF signal through an antenna and the received signal is bandpass-filtered through an analog bandpass filter. The bandpass-filtered analog signal is amplified through a Low Noise Amplifier (LNA) and then is converted into a digital baseband signal through an ADC. Since the bandpass sampling receiver does not require an analog device such as a mixer and a local oscillator, it may provide a flexible, low cost, and small wireless communication receiver. However, the typical bandpass sampling receiver may down-convert a received analog RF signal into a baseband signal of a digital format only when a carrier frequency is integer times of a sample rate in receiving a single RF signal.
Accordingly, when a signal in an arbitrary frequency band is to be received using the typical bandpass sampling receiver, a sample rate needs to be determined in order to prevent aliasing in a baseband after digital conversion. However, it is very complex to determine a sample rate to prevent aliasing and furthermore, there are cases that no solution is found for a sample rate to prevent aliasing. Therefore, the typical bandpass sampling receiver has a limitation in receiving an RF signal in an arbitrary frequency band.
Moreover, a demand for the accommodation of at least two respectively different communication standards signal using a single wireless receiver has been increased recently. Especially, a communication type such as a Software-Defined Radio (SDR) communication system requires a function for receiving an arbitrary frequency band signal. However, a typical receiver should include respectively different receiver circuits or chips according to each mode and each frequency band or channel. Therefore, a circuit structure of the typical receiver becomes complex and its unit cost becomes expensive. As a result, a new type of receiver that supports a multimode using a single receiver circuit is required.